Electric infrared heater

ABSTRACT

An electric heater for emitting infrared radiations having a plurality of insulating elements adhesively sandwiched between a pair of superimposed sheets to form a maze therein with a zigzag passageway, and a continuous infrared radiating element disposed in the passageway with terminals at both ends thereof. The sheets are composed of fibrous aluminum oxide and silicon dioxide and interstices in the sheets are filled with silicon dioxide particles to provide a good emitter of infrared radiation having an emissivity factor of about 90 percent.

United States Patent Inventor Appl. No.

Filed Patented Assignee Stanley V. Joeckei Wayne, N .J

July 24, 1969 Division of Ser. No. 600, 840, Dec. 12, 1966.

Feb. 16, 1971 Infra-Red Systems, Inc. Riverdale, NJ.

ELECTRIC INFRARED HEATER 1 Claim, 5 Drawing Figs.

U.S.Cl.

Int. Cl

Fieldoi12111:III:III.III:Ill :1 219/55 References Cited UNITED STATESPATENTS 2,787,723 4/1957 Fehr m1 2,889,445 6/1959 Wolf 219/345 3,013,89812/1961 Dempcy. 117/169X 3,031,739 5/1962 Boggs 2l9/354X 3,077,4132/1963 Campbell 117/169X 3,153,140 10/1964 Theodore et a1 219/5493,155,814 11/1964 Appleman et a1.. 219/354X 3,303,324 2/1967 Appleman219/345 3,479,490 1 1/1969 Stark 219/544 Primary Examiner-Velodymyr Y.Mayewsky Attorney-Leo C. Krazinski ABSTRACT: An electric heater foremitting infrared radiations having a plurality of insulating elementsadhesively sandwiched between a pair of superimposed sheets to form amaze therein with a zigzag passageway, and a continuous infraredradiating element disposed in the passageway with terminals at both endsthereof. The sheets are composed of fibrous aluminum oxide and silicondioxide and interstices in the sheets are filled with silicon dioxideparticles to provide a good emitter of infrared radiation having anemissivity factor of about 90 percent.

PATENTEDFEB16|97| I 3564,20";

swvm' y JON/(EL INVENTOR ATTORNEY ELECTRIC INFRARED HEATER This is adivision of application Ser'. No. 600,840 filed Dec. 12, I966.

The present invention relates to infrared heaters and, moreparticularly, to such heaters utilizing elements which have beenconverted from a heat insulating feltlike cloth material to acardboardlike material for emitting infrared radiations, and to themethod of so converting the material.

Accordingly, an object of the present invention is to provide such amethod which is simple and economical.

Another object is to provide such a method for producing elements whichare readily assembled with other elements to form the heaters.

Another object is to provide such a method which enables the elements tobe produced in any desired shape or from with a heating or infraredradiating element sandwiched therebetween.

A further object is to provide such a method for producing heaters of ashape or form adapted to enclose objects to be heated.

Other and further objects will be obvious upon an understanding of theillustrative embodiment about to be described, or will be indicated inthe appended claims, and various advantages not referred to herein willoccur to one skilled in the art upon employment of the invention inpractree.

In the drawings:

FIG. I is a fragmentary exploded perspective view of a flat heater.

FIG. 2 is a fragmentary sectional view of a section of the heater shownin FIG. 1 illustrating the heater as assembled.

FIG. 3 is a perspective view of a tubular cylindrical heater.

FIG. 4 is a perspective view of a hollow semicylindrical heater.

FIG. 5 is a perspective view of a hollow generally conical heater.

Referring now to the drawing in detail and, more particularly to FIGS. Iand 2, there is shown a heater of the type described hereinbefore whichgenerally comprises a pair of superimposed sheets and 11 having acontinuous zigzag maze l2 sandwiched therebetween and adhesively securedthereto, and a continuous infrared radiating element 14 disposed in apassageway 15 of the maze and having terminals 16 connected to theelement 14 in any suitable manner, as by a heliarc weld and extendingoutwardly of the heater.

Preferably, a sheet of aluminum (not shown) or other suitablelight-reflecting material covers the outer surface of one of the sheets10 and Il, so that radiant energy is emitted only from the other sheet.

The heater shown in FIGS. 1 and 2 may be used as a stove by placingcooking utensils thereon, or may be used as a radiant heating panel forelectrically heating buildings and the like.

In FIG. 3, a heater is shown havinga tubular cylindrical shape. Such aheater may be used for cooking frankfurters or heating other elongatedobjects placed within the heater. Heat is uniformly applied to all sidesof the object without rotating the object itself. Further, a pair ofsuch circular heaters may be concentrically arranged for cookinghamburgers, steaks and the like disposed therebetween;

In FIG. 4, a hollow semicylindrical heater is shown. This heater may beused for heating the top of an article placed thereunder.

In FIG. 5, a hollow generally conical heater is shown which has a ventor opening 17 at the apex. Such a heater may be used for roasting apiece of meat by placing the meat therein or for-,heating other objects.Here again, heat is uniformly applied from all sides and from the topwithout changing the position of the object.

The maze 12 is constructed of strips of heat insulating materialcomposed of fibrous aluminum oxide and silicon dioxide and having theconsistency of a feltlike cloth and being capable of withstandingtemperatures up to 2,300 F. Such a material is sold under the trademarkFiberfrax" by Carborundum Co.

The sheets 10 and 11 are fabricated by the method about to be describedfrom the same material of which the maze is constructed. The sheets 10and 11 are cut to a desired shape and size from a larger sheet ofmaterial. The sheets are immersed in an aqueous solution containingfinely divided silicon dioxide particles and a dispersing agent, such asan inorganic detergent. The aqueous solution preferably consists ofratio of 55 to l of the silicon dioxide particles and disbursing agent.The former is obtained under the trademark Ludox" (Dupont) and consistsof Colloidal silica as SiO Ratio wt. SiO /Na 0 95 Chloride as NaCl 0.04sulfate as Na SO 0.05

, Viscosity at 25 C. cps 3.6

pH at 25 C. 9.8

Surface area B.E.T. method M2g Silica 210.0 Approx. particle diameterTurbidity 21 The dispersing agent is obtained-under the trademarkPluronic (Wyandotte) and consists of 40 percent hydrophylicpolyoxyethylene and 60 percent polyoxypropylene.

The sheets are immersed in the above-mentioned solution for a sufficientduration of time, for example from about onehalf minute to about 4minutes, to allow the sheets to become completely saturated with thesolution and to fill the interstices with silicon dioxide particleswhile maintaining the solution at a temperature of between about F. andabout 125 F. The excess of the aqueous solution is drained from thesheets by placing the sheets on a perforated rack (not shown).Thereafter the sheets are dried slowly to remove moisture therefrom.

In the drying procedure the sheets are allowed to lose moisture slowlyfor about 24 hours at between about 80 and about F. or by subjectingthem to infrared heat for about 6 or 7 hours.

The dry sheets no longer have a feltlike consistency but will be hardand stiff, like thick cardboard. In addition, the thermal conductivityof the sheets will have changed drastically. Whereas formerly the sheetmaterial was a very good heat insulator, it now has become a relativelygood conductor of heat. Since the interstices in the original fibrousmaterial have been filled with silicon dioxide particles, the materialnow is a very good emitter of infrared radiation and has an emissivityfactor well about 90 percent.

The heater, shown in FIGS. I and 2, is constructed by arranging mazestrips, as sown, on one of the sheets and adhesively securing themthereto with a silica-alumina cement which can withstand temperatures upto 2,300 F. The passageways 15 of the maze 12 are filled with theheating element l4 and the terminals 16 thereof are secured to thesheet. The passageways 15 are filled with the cement just described tosecure the heating element 14 therein. More of the cement is placed onthe maze strips and the other sheet is superimposed to sandwich the mazeand the heating element I4 between the sheets I0 and 11. Pressure isapplied so that the sheets remain in closure contact with the mazestructure while drying the cement for several hours to produce a thintwosided infrared generator. The above silica-alumina cement preferablyconsists of:

SiO; 57.0 percent MgO 0.4

Trace Ingredients 0.2

The heaters shown in FIGS. 3 to, 5 are built by securing the maze l2 andthe heating element 14 between sheets which have not been driedcompletely but are still pliable, shaping the resulting structure to itsdesired form, and then drying the same very slowly, so that the heatinsulating properties of the maze strips will not be affected adversely.

From the foregoing description, it will be seen that the presentinvention provides an improved infrared heater and a simple andpractical method of making the same.

As various changes may be made in the form, construction, andarrangement of the parts herein, without departing from the spirit andscope of the invention and without sacrificing any of its advantages, itis to be understood that all matters are to be interpreted asillustrative and not in any limiting sense.

lclaim: v

1. An electric heater for emittinginfrared radiations comprising a pairof superimposed sheets, a plurality of insulating elements composed ofaluminum oxide and silicon dioxide and being sandwicliedrand adhesivelysecured between said sheets to form a mazetherein, said maze having azigzag passageway formed therein, and a continuous infrared radiatingelement disposed in said passageway, electrical terminals connected tothe ends of said infrared radiating elements and extending from saidinsulating maze, said sheets being composed of fibrous aluminum oxideand silicon dioxide having interstices therein filled with silicondioxide particles to provide an emitter of infrared radiation having anemissivity factor of about 90 percent, said'sheets being capable ofwithstanding 2,300 F, v

1. An electric heater for emitting infrared radiations comprising a pairof superimposed sheets, a plurality of insulating elements composed ofaluminum oxide and silicon dioxide and being sandwiched and adhesivelysecured between said sheets to form a maze therein, said maze having azigzag passageway formed therein, and a continuous infrared radiatingelement disposed in said passageway, electrical terminals connected tothe ends of said infrared radiating elements and extending from saidinsulating maze, said sheets being composed of fibrous aluminum oxideand silicon dioxide having interstices therein filled with silicondioxide particles to provide an emitter of infrared radiation having anemissivity factor of about 90 percent, said sheets being capable ofwithstanding 2,300* F.